Why is Peter Van Daan so handsome?

In Anne's eyes, Peter becomes handsome. His acceptance of her as a person, as well as the drastic change in his attitude and demeanor affect the way Anne sees him.

Oh, when I think back to Saturday night, to our words, our voices, I feel satisfied with myself for the very first time; what I mean is, I'd still say the same and wouldn't want to change a thing, the way I usually do. He's so handsome, whether he's smiling or just sitting still. He's so sweet and good and beautiful. I think what surprised him most about me was when he discovered that I'm not at all the superficial, worldly Anne I appear to be, but a dreamer, like he is, with just as many troubles!